Organic semiconductor compounds are central to the low-cost manufacturing of organic thin film transistors (“TFTs”). However, many organic semiconductor compounds suffer from either difficulties in processing in solution and/or instability in ambient conditions. In addition, certain conventional synthetic processes for preparing these organic semiconductor compounds involve multi-step reaction routes of relatively low overall yields. Thus, there is a need addressed by embodiments of the present invention for organic TFTs which incorporate organic semiconductor compounds that are solution processable and/or exhibit good stability in ambient environmental conditions. Furthermore, the present invention in embodiments provides a new process for preparing certain organic semiconductor compounds that involves fewer reaction steps and provides a higher overall yield, as compared with conventional processes.
In the literature, the term “oligomer” may convey two different definitions: one refers to a mixture of low-molecular weight compounds which consist of small numbers of repeating units of one or more chemical entities, and is therefore a subset of a polymer. The oligomer under this definition is generally characterized by number-average and weight-average molecular weights. A polymer refers to a mixture of high molecular-weight compounds consisting of large numbers of repeating units of one or more chemical entities. The distinction of low and high molecular weights to distinguish oligomer and polymer has not been clearly drawn. The other definition of “oligomer” refers to a low molecular-weight compound consisting of a specific number of repeating units of one or more chemical entities, and it is therefore characterized by a specific molecular weight. Every molecule of the oligomer under this definition is identical in all respects. We use the term “small molecular compound” to describe this class of oligomers to avoid confusion.
The following documents provide background information:
Marks et al., WO 02/09201 A1.
Aratani et al., U.S. Pat. No. 5,705,826.
Tsuyoshi Izumi et al., “Synthesis and Spectroscopic Properties of a Series of Beta-Blocked Long Oligothiophenes up to the 96 mer: Revaluation of Effective Conjugation Length,” J. Am. Chem. Soc., Vol. 125, No. 18, pp. 5286–5287 and S1–S6 (Apr. 10, 2003).
Francis Garnier et al., “Molecular Engineering of Organic Semiconductors: Design of Self-Assembly Properties in Conjugated Thiophene Oligomers,” J. Am. Chem. Soc., Vol. 115, No. 19, pp. 8716–8721 (1993).
Howard Katz et al., “Synthesis, Solubility, and Field-Effect Mobility of Elongated and Oxa-Substituted alpha, omega-Dialkyl Thiophene Oligomers. Extension of ‘Polar Intermediate’ Synthetic Strategy and Solution Deposition on Transistor Substrates,” Chem. Mater., Vol. 10, No. 2, pp. 633–638 (1998).
V. M. Niemi et al., “Polymerization of 3-alkylthiophenes with FeCl3,” Polymer, Vol. 33, No. 7, pp. 1559–1562 (1992).
A. Afzali et al., “An Efficient Synthesis of Symmetrical Oligothiophenes: Synthesis and Transport Properties of a Soluble Sexithiophene Derivative,” Chem. Mater., Vol. 14, No. 4, pp. 1742–1746 (Mar. 6, 2002).
X. Michael Hong et al., “Thiophene-Phenylene and Thiophene-Thiazole Oligomeric Semiconductors with High Field-Effect Transistor On/Off Ratios,” Chem. Mater., Vol. 13, No. 12, pp. 4686–4691 (2001).
Beng Ong et al., U.S. application Ser. No. 10/042,358 (Attorney Docket No. D/A1332), filed Jan. 11, 2002, titled “POLYTHIOPHENES AND DEVICES THEREOF,” which has been published as US Published Application 2003/0160230.
Beng Ong et al., U.S. application Ser. No. 10/042,342 (Attorney Docket No. D/A1333), filed Jan. 11, 2002, titled “POLYTHIOPHENES AND DEVICES THEREOF,” which has been published as US Published Application 2003/0160234.
Beng Ong et al., U.S. application Ser. No. 10/042,356 (Attorney Docket No. D/A1334), filed Jan. 11, 2002, titled “POLYTHIOPHENES AND DEVICES THEREOF,” which issued as U.S. Pat. No. 6,621,099.